Shifting mechanism for dual-action power-operated abrading tool



March 5, 1968 5, ENDERS 3,371,451

SHIFTING MECHANISM FOR DUAL-ACTION I POWER-OPERATED ABRADING TOOL FiledMarch 28, 1966 2 Sheets-Sheet 1 INVENTOR SHERWOOD G. ENDERS BY ,gnd.

ATTORNEY March '5, 1968 s. G. ENDERS SHIFTING MECHANISM FOR DUAL -ACTIONPOWER-OPERATED ABRADING TOOL Filed March 28, 1966 2 Sheets-Sheet 2INVENTOR ATTORNEY United States Patent 3 3711. 451 srnrrmo Mncnariusrfinon nUaL-Acrrort POWER-OPERATEE AERADENG TOUL faherwood G. Enders,Bowleys Quarters, Md assignor to The Black and Decker ManufacturingCompany,

Toe/son, Md, a corporation of Maryland Filed Mar. 28, M66, Ser. No.538,004 7 Claims. ((15. 5l--17t)) The present invention relates to ashifting mechanism for a dual-action portable electric sander, wherebythe tool platen may have either a substantailly straight-linereciprocation or else an orbital reciprocation; and more particularly,the present invention constitutes an improvement over the mechanismdisclosed in the co-pending Sheps application, Ser. No. 538,005, filedMar. 28, 1966, entitled, Dual-Action Power-Operated Abrading Tool, andassigned to the assignee of the present invention.

The present invention may be used in conjunction with a portablepower-operated abrading tool, such as a portable electric sander, of thetype comprising a housing, a platen resiliently mounted below thehousing, a pivot arm between the housing and the platen, the pivot armhaving a pair of ends, one of which is pivotally mounted on the platenand the other of which is free, and a driving eccentric connected to thepivot arm intermediate the ends of the arm, the driving eccentric beingjournaled or disposed along a substantially vertical axis, whereby thepivot arm oscillates substantially in a horizontal plane above theplaten, and whereby the platen has a substantially straight-linereciprocation. If the free end of the pivot arm is restrained againstfurther oscillation, such as by exerting a vertical clamping force asdescribed in the aforesaid Sheps application, then the straight-linereciprocation of the platen is converted into an orbital reciprocation;and conversely, when the vertical clamping force is released and thefree end of the pivot arm is no longer restrained, then the orbitalreciprocation of the platen is converted back into a substantiallystraight-line reciprocation.

The present invention constitutes an improvement in the guiding andselective restraining mechanism for the free end of the oscillatingpivot arm; and this improvement comprises, in combination, a bearingguide having a slot receiving the free end of the pivot arm, meanssupporting the bearing guide on the platen and journaling the same forpivotal movement about a substantially horizontal axis, whereby the slotin the bearing guide angularly adjusts to the free end of the pivot arm,and means carried on the platen for selectively restraining the free endof the pivot arm against oscillation in a horizontal plane, whereby thestraight-line reciprocation of the platen is converted into an orbitalreciprocation.

It is an object of the present invention to provide an improved guidingand restraining mechanism, wherein the bearing guides for the free endof the oscillating pivot arm may aline themselves, that is, angularlyadjust to the pivot arm, and wherein the clamping means for selectivelyrestraining the free end of the pivot arm comprises a clamping memberwhich is separate from the bearing guides, thereby resulting in animproved mechanism having the advantages of increased reliability anddurability over an extended period of operation.

In accordance with a preferred embodiment of the present invention, athreaded stud is secured on the platen and projects verticallytherefrom. A pair of bearing guide supports are piloted on the stud.These bearing guide supports are substantially identical to one anotherand comprise a top bearing guide support and a bottom bearing guidesupport, the latter being supported upon the platen. The bearing guidesupports have respective curved portions. The curved portion of one iscomplementary to 337L451 Patented Mar. 5, 1968 and confronts the curvedportion of the other so as to form a generally cylindrical bearing seat.A bearing guide is journaled in the seat and is restrained against axialdisplacement therefrom. The bearing guide has a slot, substantially in ahorizontal plane, for receiving the free end of the pivot arm.Preferably, a pair of bearing guides are provided, spaced apart from oneanother. With this arrangement, the slots in the bearing guidesangularly adjust, individually, to the free end of the pivot arm. Aclamp member is piloted on the stud above the top bearing guide supportand has a clamping portion disposed between the spaced-apart bearingguides and above the free end of the pivot arm. A lever has a threadedportion engaging the stud above the clamp member, thereby selectivelyexerting a vertical clamping pressure which restrains the free end ofthe pivot arm between the clamp member portion and the bottom surfacesof the slots in the respective bearing guides. Preferably, a springmember is piloted on the stud between the top bearing guide support andthe clamp member, thereby preventing substantial contact between theclamp member portion and the free end of the pivot arm in the normalunrestrained position of the pivot arm.

In accordance with another aspect of the present invention, the improvedstructure comprises, in combination, a first member having a means forslidably supporting the free end of the pivot arm, means supporting thefirst member on the platen and journaling the same for pivotal movementabout a substantially horizontal axis, whereby the first memberangularlty adjusts to the free end of the pivot arm, a second member forselectively clamping the free end of the pivot arm against the firstmember, and resilient means constantly urging the second member awayfrom the free end of the pivot arm in its unrestrained position.

These and other objects of the present invention will become apparentfrom a reading of the following specification, taken in conjunction withthe enclosed drawings, in which:

FIGURE 1 is a side elevation of a typical portable power-operatedabrading tool with which the teachings of the present invention may findparticular utility;

FIGURE 2 is an enlarged top plan view of the platen assembly, theconventional four rubber posts being shown in section;

FIGURE 3 is a section view, taken along the lines 33 of FIGURE 2, thefour rubber posts being omitted for clarity of illustration, and theview showing the manner in which the pivot arm is pivotally mounted onthe platen, the manner in which the driving eccentric is preferablyjournaled in a bearing retained intermediately of the ends of the pivotarm, and the improved structure of the present invention for guiding andselectively restraining the free end of the pivot arm;

FIGURE 4 is a section view, taken along the lines 44 of FIGURE 2,showing the manner in which the free end of the pivot arm is guided inthe bearing guides, and further showing the manner in which the clampmember portion exerts a vertical clamping pressure to restrain the freeend of the pivot arm against the lower surfaces of the slots in therespective bearing guides;

FIGURES 5a and 5b illustrate the manner in which the bearing guides andthe respective slots therein may angularly adjust to (or pivot inresponse to) the posi tion of the free end of the oscillating pivot arm;

FIGURE 6 is an exploded perspective of the improved structure of thepresent invention; and

FIGURE 7 is a modification illustrating the manner in which the bearingguide may be resiliently supported in the bearing guide supports for thepurpose of adjusting to the position of the pivot arm in a mannerequivalent to the embodiment of FIGURES 5a and 5b.

With reference to FIGURE 1, there is illustrated a portable electricsander or abrading tool in which the improved structure of the presentinvention may be incorporated. The tool 10 generally comprises a motorhousing 11, a flanged skirt 12, a rear handle 13 having an electricswitch 14 for energization of the unit from an electrical line cord 15,a front handle 16 to assist in guiding and controlling the tool, and aplaten assembly, denoted generally as at 17, and resiliently supportedbelow the housing.

With reference to FIGURES 2 and 3, the platen assembly 17 includes aconventional pad 18 provided with a sheet-metal backing 19. The pad 18is resiliently mounted to the tool housing by means of four rubber posts20, which are retained to the backing 19 by means of respective brackets21. Each bracket 21 has a curved portion 22 which journals a cylindricalrod 23. The rod 23 has spaced-apart knurled portions 24 and ascrewdriver slot 25 at its ends. With this arrangement, the rod 23provides a convenient clamp for the typical abrasive paper used with atool of this type. The manner in which the rubber posts 20 are retainedin the housing of the tool, the manner in which the bracket .21 securesor traps a respective pair of posts to the backing 1'9, and the mannerin which the paper clamp subassembly is provided by the rod 23, form nopart of the present invention, but rather are described in detail in theco-pending Enders application, Ser. N0. 348,124, filed Feb. 28, 1964,entitled Oscillating Piaten for Abradin-g Tool and assigned to theassignee of the present invention, now Patent No. 3,336,- 702, datedAug. 22, 1967.

With reference again to FIGURES 2 and 3, a pivot arm 26 is disposedabove the platen and functions as an intermediate driving member betweenthe driving eccentric and the platen. The pivot arm ha one end pivotedto the platen, and carries a bearing intermediate its ends forjournaling a driving eccentric. With this arrangement, the free end ofthe pivot arm, being unrestrained, oscillates in a generally horizontalplane above the platen, and the platen has a substantially straightdinereciprocation. In accordance with the present invention, the free end ofthe pivot arm is slidably guided within one or more bearing guides, andthe bearing guides are preferably journaled for pivotal movement inorder to adjust to the free end of the pivot arm. Means are alsoprovided for restraining the free end of the arm, thereby converting thestraight-line reciprocation of the platen into an orbital reciprocation.

With particular reference to FIGURE 3, the preferred means for pivotingthe front end of the pivot arm 26 to the platen is as follows: Aninternally-threaded stud 27 is secured to the platen by means of a screw28, the latter also securing the respective bracket 21 to the platen. Aflanged bushing 29 is piloted on the stud 27. The flanged bushingreceives the collar portion 26a of the pivot arm 26. A washer retainer30 is also piloted on the stud above the collar 26a. Completing theassembly, the retainer washer 30 is retained by means of a washer 31 andscrew 32, the latter being received within the stud 27. Both the flangedbushing 29 and the retainer washer 30 are preferably molded of ananti-friction plastic material. Any suitable means, however, may be usedto pivot the front end of the pivot arm 26 to the platen.

With reference again to FIGURE 3, the preferred means for driving thepivot arm 26 is as follows: A bearing retainer 33 is securedintermediately the ends of the pivot arm 26 by means of screws 34. Thebearing retainer 33 has a partially-completed spherical seat 33a forreceiving a spherical sleeve bearing 35. A driving eccentric 36 isjournaled within the bearing 35 along a substantially vertical axis, andthe driving eccentric 36 is connected with the motor (not shown) of thetool. The manner of mounting the bearing retainer 33, the manner inwhich the bearing retainer accommodates usage of a spherical bearing 35,and the related structure of the driving eccentric 36, form no part ofthe present invention,

4 but rather are described in detail in the Enders Patent 3,199,251entitled Driving Mechanism for Abrading Tool, issued Aug. 10, 1965, andassigned to the assignee of the present invention.

With reference again to FIGURES 2 and 3, and with further reference toFIGURES 6, the improved structure of the present invention is a follows:A threaded stud 37 is secured on the other end of the pad 1 8 by meansof a screw 38, the latter also securing the respective bracket 21 to thepad. A spacer washer 39 is piloted on the lower portion of the stud 37.A pair of bearing guide supports (comprising a top bearing guide support40 and a bottom bearing guide suport 41) are also piloted on the lowerportion of the stud 37, and are retained between the spacer washer 39and a shoulder 37a formed on the stud. The bearing guide supports 40, 41have respective curved portions 42 and 43. Preferably, the respectivecurved portions 42, 43 of the bearing guide supports 40, 41 areinterrupted, see FIGURE 2, so as to form spaced-apart curved portions.These curved portions are complementary to one another and confront oneanother to form respective seats for journaling respective bearingguides 44. In the particular embodiment shown in the drawings, twospaced bearing guides 44 are employed, one in each of the respectiveseats. The bearing guides 44 have slots 45 formed therein, and theseslots 45 are substantially aligned with one another in a generallyhorizontal plane for receiving the raised lip portion 261) formed on thefree end of the pivot arm 26. Preferably, the bearing guides 44 areformed of an anti-friction material and have respective flanges 46 forpreventing axial displacement of the bearing guides 44 from theirrespective seats in the bearing guides supports 40, 41. Preferably, butno necessarily, the respective axes of the bearing guides 44 intersectone another so as to conform to the generally arcuate plan view, seeFIGURE 2, of the raised lip 26]; on the free end of the pivot arm 26.

With reference to FIGURES 5a and 5b, it will be appreciated that thebearing guides 44 are journaled for pivotal movement about asubstantially horizontal axis, and in this manner the respective slots45 in the bearing guides 44 may angularly adjust, individually, to theraised lip 26b on the free end of the pivot arm 26. In a sense, thebearing guides 44 may be said to be self-alining in relation to thehorizontally-disposed oscillating pivot arm 26. In FIGURES 5a and 5b,the extreme positions of the bearing guides 44 are shown forillustrative purposes. In FIGURE 5a, the bearing guide 44 has rotatedclockwise, as viewed in the drawing, to accommodate the somewhat skewedposition of the free end of the pivot arm 26. On the other hand, inFIGURE 51) the bearing 44 has rotated counterclockwise, as viewed in thedrawing, to accommodate the reversely skewed position of the free end ofthe pivot arm 26. With this arrangement, the free end of the oscillatingpivot arm 26 is smoothly guided in its unrestrained position, and themanner in which the bearing guides 44 are mounted on the platen relievesor compensates for any manufacturing variations or toleranceaccumulations which might otherwise offset or unduly restrain the freeend of the pivot arm.

In order to restrain the free end of the pivot arm, whenever desired forthe purpose of shifting the reciprocation Of the platen into an orbitalmode, a clamping means is provided which basically is separate from thebearing guides 44, the latter serving to slidably guide the free end ofthe arm. In accordance with the teachings of the present invention, aclamp washer 47 is piloted on an unthreaded portion of the stud 37 abovethe top bearing guide support 40. Preferably, the clamp washer 47 isintegrally molded of a suitable anti-friction material. A clamp support48, see FIGURE 6, is disposed above the clamp washer 47. The clampsupport 48 has an aperture 48a receiving the collar 47a of the clampWasher 47, and the clamp support 48 further has a pair of cars 49 whichstraddle the rear portion of the clamp washer 47. This prevents relativerotation between the clamp washer 47 and its clamp support 48. The clampwasher 47 has a clamping portion 50 which, see FIGURE 2, is receivedbetween the bearing guides 44. Completing the assembly, a lever 51 has athreaded portion, such as a Weld nut 52, received on the threadedportion of the stud 37 above the clamp support 48.

In operation, when the lever 51 is pivoted through an acute angle, theclamping portion 50 of the clamp washer 47 bears down upon the free endof the pivot arm 26, and as shown in FIGURE 4, the arm is retainedbetween the clamping portion 50 and the bottom surfaces of therespective slots 45 in the bearing guides 44. This restrains the freeend of the pivot arm, precludes further oscillation of the arm in ahorizontal plane above the platen 17, and converts the substantiallystraight-line reciprocation of the platen into an orbital reciprocation,Conversely, when the lever 51 is pivoted in the reverse direction, theclamping portion 50 of the clamp washer 47 is lifted away from the freeend of the pivot arm 26, the arm is in its normally unrestrainedposition, and the platen 17 has a substantially straight-linereciprocation.

In accordance with another feature of the present invention, a springmember 53 (which may be formed of sheet metal) is preferably piloted onthe stud 37 and is lodged between the top bearing guide support 40 andthe clamp washer 47. This provides a resilient means for preventing theclamping portion 50 of the clamp washer 47 (and the weight of it and itsassociated parts) from interfering with or otherwise restraining thefree arm of the pivot arm 26 in its normally unrestrained position.

Preferably, as disclosed in the aforementioned copending Shepsapplication, a molded-plastic wrench member 54 is provided, see FIGURE6, and the wrench 54 has a recess 55 engaging the end of the lever 51for the purpose of actuating the lever.

With reference to FIGURE 7, a modification is illus trated, wherein thebearing guide 44 is resiliently mounted between the bearing guidesupports 40 and 41' by means of a substantially U-shaped resilientmember 56. This allows the bearing guide 44' to move, pivot, or cockslightly to accommodate the position of the free end of the oscillatingpivot arm. The operation of the resiliently mounted bearing guide 44 issubstantially equivalent to what has been described previously withreference to the embodiment of FIGURE 6.

Obviously, many modifications may be made without departing from thebasic spirit of the present invention; and accordingly, within the scopeof the appended claims, the invention may be practiced other than hasbeen specifically described herein.

I claim:

1. In a portable power-operated abrading tool having a housing, a platenresiliently mounted below the housing, a pivot arm between the housingand the platen, the pivot arm having a pair of ends, one of which ispivotally mounted on the platen and the other of which is free, abearing mounted on the pivot arm intermediate its ends, and a drivingeccentric journaled in the bearing along a vertical axis, whereby thepivot arm oscillates substantially in a horizontal plane above theplaten, and whereby the platen has a straight-line reciprocation, theimprovement which comprises:

(a) a bearing guide having a slot receiving the free end of the pivotarm;

(b) means supporting the bearing guide on the platen and journaling thesame for pivotal movement about a substantially horizontal axis, wherebythe slot in the bearing guide angularly adjusts to the free end of thepivot arm; and

(c) means carried on the platen for selectively restraining the free endof the pivot arm against oscillation in a horizontal plane, whereby thestraight-line reciprocation of the platen is converted to an orbitalreciprocation.

2. In a portable power-operated abrading tool having a housing, a platenresiliently mounted below the housing, a pivot arm between the housingand the platen, the pivot arm having a pair of ends, one of which ispivotally mounted on the platen and the other of which is free, abearing mounted on the pivot arm intermediate its ends, and a drivingeccentric journaled in the bearing along a vertical axis, whereby thepivot arm oscillates substantially in a horizontal plane above theplaten, and whereby the platen has a straight-line reciprocation, theimprovement in means for guiding the free end of the pivot arm and forselectively restraining the same against further movement, therebyconverting the straight-line reciprocation of the platen to an orbitalreciprocation, which improvement comprises:

(a) a pair of spaced-apart bearing guides having respective slots alinedwith one another in a horizontal plane and receiving the free end of thepivot arm;

(b) means supporting the bearing guides on the platen and journaling thesame for pivotal movement about respective substantially-horizontalaxes, whereby the slots in the bearing guides individually angularlyadjust to the free end of the pivot arm; and

(c) a clamp member carried on the platen and having a portion disposedbetween the spaced-apart bearing guides for selectively restraining thefree end of the pivot arm.

3. in a portable power-operated abrading tool having a housing, a platenresiliently mounted below the housing, a pivot arm between the housingand the platen, the pivot arm having a pair of ends, one of which ispivotally mounted on the platen and the other of which is free, abearing mounted on the pivot arm intermediate its ends, and a drivingeccentric journaled in the bearing along a vertical axis, whereby thepivot arm oscillates substantially in a horizontal plane above theplaten, and whereby the platen has a straight-line reciprocation, theimprovement which comprises:

(a) a threaded stud secured on the platen and projecting verticallytherefrom;

(b) a pair of bearing guide supports piloted on the stud;

(c) said bearing guide supports being substantially identical to oneanother and comprising a top bearing guide support and a bottom bearingguide support, the latter being supported by the platen;

(d) said bearing guide supports having respective spaced-apart curvedportions, the curved portions of one being complementary to andconfronting the curved portions of the other to form a pair ofspacedapart cylindrical bearing seats;

(e) a pair of respective cylindrical bearing guides journaled in thebearing seats and restrained against axial displacement therefrom;

(f) said bearing guides having respective slots, alined with one anotherin a substantially horizontal plane, and receiving the free end of thepivot arm, whereby the slots in the bearing guides individuallyangularly adjust to the free end of the pivot arm;

(g) a clamp member piloted on the stud above the top bearing guidesupport and having a clamping portion disposed between the spaced-apartbearing guides and above the free end of the platen; and

(h) a lever having a threaded portion engaging the stud above the clampmember, thereby selectively exerting a vertical clamping pressure on thefree end of the pivot arm.

4. The improvement of claim 3, wherein:

(a) the bearing guides are journaled for pivotal movement aboutrespective axes which intersect one another.

5. The improvement of claim 3, wherein:

(a) a clamp support member is piloted on the stud between the clampmember and the lever;

(b) said clamp support member being keyed to the clamp member to preventrelative rotation therebetween.

6. The improvement of claim 3, wherein:

(a) a spring member is piloted on the stud between the top bearing guidesupport and the clamp member, thereby preventing substantial contactbetween the clamp member portion and the free end of the pivot arm inits unrestrained position.

7. In a portable power-operated abrading tool having a housing, a platenresiliently mounted below the housing, a pivot arm between the housingand the platen, the pivot arm having a pair of ends, one of which ispivotally mounted on the platen and the other of which is free, abearing mounted on the pivot arm intermediate its ends, and a drivingeccentric journaled in the bearing along a vertical axis, whereby thepivot arm oscillates substantially in a horizontal plane above theplaten, and whereby the platen has a straight-line reciprocation, theimprovement in means for guiding the free end of the pivot arm and forselectively restraining the same against further movement, therebyconverting the straight-line 8 reciprocation of the platen to an orbitalreciprocation, which improvement comprises:

(a) a first member having means for slidably supporting the free end ofthe pivot arm; (b) means supporting the first member on the platen andjournaling the same for pivotal movement about a substantiallyhorizontal axis, whereby the first member angularly adjusts to the freeend of the pivot arm; (c) a second member for selectively clamping thefree end of the pivot arm against the first member; and (d) resilientmeans constantly urging the second member away from the free end of thepivot arm in its unrestrained position.

References Cited UNITED STATES PATENTS 2,885,833 5/1959 Neff 51-17OLESTER M. SWINGLE, Primary Examiner.

1. IN A PORTABLE POWER-OPERATED ABRADING TOOL HAVING A HOUSING, A PLATENRESILIENTLY MOUNTED BELOW THE HOUSING, A PIVOT ARM BETWEEN THE HOUSINGAND THE PLATEN, THE PIVOT ARM HAVING A PAIR OF ENDS, ONE OF WHICH ISPIVOTALLY MOUNTED ON THE PLATEN AND THE OTHER OF WHICH IS FREE, ABEARING MONTED ON THE PIVOT ARM INTERMEDIATE ITS ENDS, AND A DRIVINGECCENTRIC JOURNALED IN THE BEARING ALONG A VERTICAL AXIS, WHEREBY THEPIVOT ARM OSCILLATES SUBSTANTIALLY IN A HORIZONTAL PLANE ABOVE THEPLATEN, AND WHEREBY THE PLATEN HAS A STRAIGHT-LINE RECIPROCATION, THEIMPROVEMENT WHICH COMPRISES: (A) A BEARING GUIDE HAVING A SLOT RECEIVINGTHE FREE END OF THE PIVOT ARM; (B) MEANS SUPPORTING THE BEARING GUIDE TOTHE PLATEN AND JOURNALING THE SAME FOR PIVOTAL MOVEMENT ABOUT ASUBSTANTIALLY HORIZONTAL AXIS, WHEREBY THE SLOT IN THE BEARING GUIDEANGULARLY ADJUSTS TO THE FREE END OF THE PIVOT ARM; AND (C) MEANSCARRIED ON THE PLATEN FOR SELECTIVELY RESTRAINING THE FREE END OF THEPIVOT ARM AGAINST OSCILLATION IN A HORIZONTAL PLANE, WHEREBY THESTRAIGHT-LINE RECIPROCATION OF THE PLATEN IS CONVERTED TO AN ORBITALRECIPROCATION.